Integrated optical device

ABSTRACT

An improved integrated optical device ( 5   a - 5   g ) is disclosed containing first and second devices ( 10   a - 10   g   ; 15   a   , 15   e ), optically coupled to each other and formed in first and second different material systems. One of the first or second devices ( 10   a - 10   g   , 15   a   , 15   e ) has a Quantum Well Intermixed (QWI) region ( 20   a   , 20   g ) at or adjacent a coupling region between the first and second devices ( 10   a - 10   g   ; 15   a   , 15   e ). The first material system may be a III-V semiconductor based on Gallium Arsenide (GaAs) or Indium Phosphide (InP), while the second material may be Silica (SiO 2 ), Silicon (Si), Lithium Niobate (LiNbO 3 ), a polymer, or glass.

FIELD OF INVENTION

This invention relates to an improved integrated optical device oroptoelectronic device, and particularly to hybrid integration of devicesformed in different material systems. For example, hybrid integration ofIII-V semiconductor devices with passive waveguide structures.

BACKGROUND TO INVENTION

Hybrid integration of III-V semiconductor components with passivewaveguides is of increasing importance as a method of increasing thefunctionality of integrated optical and photonic systems. Applicationsinclude: optical communication systems, optical sensing applications,and optical data processing.

A fundamental problem in hybrid integration is that the semiconductorelement has a higher refractive index than the passive waveguide. In thecase of a III-V semiconductor component integrated on a planar Silica(SiO₂) platform, the refractive indices are typically around 3.6 for thesemiconductor and 1.5 for the Silica. This refractive index differencecauses a number of problems, e.g. there is a high reflection coefficientat the interface between the two devices, and the mode size in eachdevice is different. Both of these effects result in a loss in opticalpower, reduced coupling efficiency between the two devices, andscattering of light, and undesirable reflections.

It is an object of the present invention to obviate or at least mitigateone or more of the aforementioned problems in the prior art.

Further objects of various embodiments of the present invention include:

enablement of hybrid integration to be carried out, while ensuring goodmode matching between active and passive sections;

ease of manufacture;

low loss coupling between active and passive sections.

SUMMARY OF INVENTION

According to a first aspect of the present invention there is providedan integrated optical device including first and second devicesoptically coupled one to the other and formed in first and seconddifferent material systems, at least one of the first or second deviceshaving a Quantum Well Intermixed (QWI) region at or adjacent a couplingregion between the first and second devices.

Quantum Well Intermixing (QWI) permits a postgrowth modification to theabsorption edge of Multiple-Quantum Well (MQW) material, and thereforeprovides a flexible, reliable, simple, and low-cost approach compared tocompeting integration schemes such as selective area epitaxy orselective etching and regrowth.

Quantum Well Intermixing (QWI) provides a means of tuning an absorptionband edge controllably in Quantum Well (QW) structures, and may beutilized to fabricate low-loss optical interconnects betweenmonolithically integrated optical devices or integrated optoelectronicdevices.

The first material system may be a III-V semiconductor material system.The III-V semiconductor material may be selected from or include one ormore of: Gallium Arsenide (GaAs), Aluminium Gallium Arsenide (AlGaAs),Indium Phosphide (InP), Gallium Arsenide Phosphide (GaAsP), AluminiumGallium Arsenide Phosphide (AlGaAsP), Indium Gallium Arsenide Phosphide(InGaAsP), or the like.

The second material system may be a non III-V semiconductor material.The second material system may be selected from: Silica (SiO₂), Silicon(Si), Lithium Niobate (LiNbO₃), a polymer, a glass, or the like, any ofwhich may be doped with optically active material.

The first device may be or include an active device component, such as alaser diode, light emitting diode (LED), optical modulator, opticalamplifier, optical switch, or switching element, optical detector (egphotodiode), or the like. The first device may also include a passivedevice compound such as a passive waveguide.

The second device may be, or include a passive component such as apassive waveguide.

Preferably, the coupling region provides means for at leastsubstantially mode matching between the first and second devices.

In one arrangement the first device provides the Quantum Well Intermixed(QWI) region.

In the one arrangement the mode matching means may comprise a waveguideprovided in the first device which waveguide may be a “tapered”waveguide providing a linear change in width, a non-linear change inwidth, and/or a “periodic” or “a-periodic” segmentation.

Preferably, the coupling region provides anti-reflection means at ornear an interface between the first and second devices.

The anti-reflection means may comprise or include an anti-reflectioncoating on a facet of the first device provided at the interface betweenthe first and second devices.

The anti-reflection means may also comprise or include facets of thefirst and second devices provided at the interface between the first andsecond devices, the facets being formed at an (acute) angle to anintended direction of optical transmission. The facets may therefore bereferred to as “angled facets”.

In a preferred embodiment a first waveguide section in the first deviceand preferably also a second waveguide section in the second deviceis/are bent.

The integrated optical device may be adapted to operate in a wavelengthregion of about 600 to 1300 nm or of about 1200 to 1700 nm.

According to a second aspect of the present invention, there is providedan integrated optical circuit, optoelectronic integrated circuit, orphotonic integrated circuit including at least one integrated opticaldevice according to the first aspect of the present invention.

According to a third aspect of the present invention there is providedan apparatus including at least one integrated optical device, the atleast one integrated optical device providing first and second devicesoptically coupled one to the other and formed in first and seconddifferent material systems, one of the first or second devices having aQuantum Well Intermixed (QWI) region at or adjacent a coupling regionbetween the first and second devices.

According to a fourth aspect of the present invention there is provideda method of providing an integrated optical device having hybridintegration of first and second devices formed in first and seconddifferent material systems comprising:

providing one of the first or second devices with a Quantum WellIntermixed (QWI) region at or adjacent a coupling region between thefirst and second devices.

The Quantum Well Intermixed (QWI) region may be formed from a number oftechniques, but preferably by a universal damage induced technique,Impurity Free Vacancy Diffusion (IFVD).

In a preferred embodiment, the Quantum Well Intermixed (QWI) region maybe formed in the first device by intermixing a Quantum Well(s) (QW) in acore optical guiding layer of the first device, e.g. by Impurity FreeVacancy Diffusion (IFVD).

When performing IFVD, a dielectric, e.g. SiO₂ layer or film, may bedeposited upon a top cap layer of the a III-V semiconductor material ofthe first device. Subsequent rapid thermal annealing of thesemiconductor material causes bonds to break within the semiconductoralloy, e.g. Gallium ions or atoms which are susceptible to Silica(SiO₂), to dissolve into the Silica so as to leave vacancies in the caplayer. The vacancies then diffuse through the semiconductor materialinducing layer intermixing, e.g. in the Quantum Well(s) (QW).

IFVD has been reported in “Quantitative Model for the Kinetics OfCompositional Intermixing in GaAs—AlGaAs Quantum—ConfinedHeterostructures,” by Helmy et al, IEEE Journal of Selected Topics inQuantum Electronics, Vol. 4, No. 4, Jul./Aug. 1998, pp. 653-660, thecontent of which is incorporated herein by reference.

According to a fifth aspect of the present invention there is provided afirst device according to the first aspect of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, and with reference to the accompanying diagrams, whichare:

FIG. 1( a) a schematic plan view of a first semiconductor chipintegrated with a passive photonic integrated circuit (PIC) according toa first embodiment of the present invention;

FIGS. 1( b)-(d) schematic plan views of second, third and fourthsemiconductor chips integratable with a passive photonic integratedcircuit (PIC) similar to or the same as that of FIG. 1( a) according tothe present invention;

FIG. 2( a) a schematic plan view of a fifth semiconductor chip accordingto the present invention;

FIG. 2( b) a schematic plan view of the fifth semiconductor chip of FIG.2( a) integrated with a passive photonic integrated circuit (PIC)according to a fifth embodiment of the present invention;

FIG. 3 a schematic cross-sectional end view showing a possible layerstructure of a semiconductor chip according to a sixth embodiment of thepresent invention;

FIG. 4 a schematic perspective view from one end, above and to one sideof the semiconductor chip of FIG. 3;

FIG. 5 a schematic perspective view from one end, above and to one sideof a semiconductor chip according to a seventh embodiment of the presentinvention.

DETAILED DESCRIPTION

Referring initially to FIG. 1( a) there is illustrated an integratedoptical device, generally designated 5 a, according to a firstembodiment of the present invention and providing the first and seconddevices 10 a, 15 a respectively, the first and second devices 10 a, 15 abeing optically coupled one to the other and formed in first and seconddis-similar material systems, at least one of the first or seconddevices 10 a, 15 a having a Quantum Well Intermixed (QWI) region 20 a ator adjacent a coupling region 21 a between the first and second devices10 a, 15 a.

In this embodiment the first materials system is a III-V semiconductormaterial system based on either Gallium Arsenide (GaAs) or IndiumPhosphide (InP). For example the III-V semiconductor material may beselected or include one or more of: Gallium Arsenide (GaAs), AluminiumGallium Arsenide (AlGaAs), and Indium Phosphide (InP), Gallium ArsenidePhosphide (GaAsP), Aluminium Gallium Arsenide Phosphide (AlGaAsP),Indium Gallium Arsenide Phosphide (InGaAsP), or the like. The integratedoptical device 5 a may therefore be adapted to operate in the so-called“short” wavelength region of 600 to 1300 nm, or the so-called “long”wavelength region of 1200 to 1700 nm.

The second material system is a non III-V semiconductor material and canbe selected from Silica (SiO₂), Silicon (Si), Lithium Niobate (LiNbO₃),a polymer, glass or the like.

The first device 10 a comprises an active device component 22 a,selected from a laser diode, light emitting diode (LED), opticalmodulator, optical amplifier, optical switching element, opticaldetector (eg photodiode), or the like. The active device component 22 ais spaced from the Quantum Well Intermixed (QWI) region 20 a, the activedevice component 22 a, and passive QWI region 20 a being in opticalcommunication one with the other via a waveguide 23 a such as a ridgewaveguide.

The second device 15 a in this embodiment includes a passive devicecomponent in the form of a passive waveguide 16 a.

The coupling region 21 a provides anti-reflection means at or near aninterface between the first and second devices 10 a, 15 a. Theanti-reflection means comprise anti-reflection coating 25 a on an endfacet on first device 10 a provided at the interface between the firstand second devices 10 a, 15 a.

In a modification the anti-reflection means may also comprise facets ofthe first and second devices 10 a, 15 a provided at the interfacebetween the first and second devices 10 a, 15 a, the facets being formedat an acute angle to the intended direction of the optical transmissionalong waveguides 23 a, 16 a. In such a modification the facets may bereferred to as “angled facets”.

Referring now to FIG. 1( b) there is illustrated a second embodiment ofa first device 10 b comprising part of an optically integrated deviceaccording to the present invention, like parts of the device 10 b beingidentified by the same numerals as those for the first embodiment, butsuffixed “b”. In this second embodiment the waveguide 23 b includes acurved portion 30 b so as to improve optical coupling between the firstdevice 10 b and a second device (not shown), by reduction of reflectionsat the interface between the first device 10 b and the second device.

Referring now to FIG. 1( c), there is illustrated a third embodiment ofa first device, generally designated 10 c, which may be a part of anoptically integrated device according to an embodiment of a presentinvention. The device 10 c is similar to the device 10 a of the firstembodiment, and like parts are identified by like numerals, but suffixed“c”. However, as can be seen from FIG. 1( c), the waveguide 23 cincludes at an end adjacent the coupling region to the second device(not shown) a tapered region 30 c which, in use, causes an optical mode“M” transmitted along the waveguide 23 c to expand as it traverses theoptical waveguide 23 c and is output from the first device 10 c from thetapered region 30 c. The converse of course applies for optical couplingto the first device 10 c from the second device (not shown).

Referring now to FIG. 1( d), there is shown a fourth embodiment of afirst device 10 d comprising part of an optically integrated deviceaccording to an embodiment of the present invention. The first device 10d is substantially similar to the device 10 a of the first embodiment,like parts being identified by like numerals but suffixed “d”. However,in the first device 10 d, the waveguide 23 d includes at an end adjacenta coupling region to a second device (not shown) a curved and taperedregion 30 d. The first device 10 d therefore combines the features ofthe embodiments of FIGS. 1( b) and (c).

It will be appreciated that in order to control electronically the firstdevices 10 a-10 d, an electrical contact (metallization) will befabricated on a surface of the waveguide 23 a-23 d, while a furtherelectrical contact (metallization) will be provided on an opposingsurface of the device 10 a-10 d.

It will be appreciated that the modifications shown in the second, thirdand fourth embodiments 10 b, 10 c, 10 d, seek to improve opticalcoupling between the first device 10 b, 10 c, 10 d, and a second device(not shown).

It will also be appreciated that the intermixed region 20 a to 20 b actsto prevent, or at least reduce, optical absorption in the intermixedregion 20 a-20 d adjacent to the coupling region 21 a-21 d. This isparticularly so in the curved tapered waveguide section 30 b.

It will further be appreciated that although herein above the waveguidesections 30 c and 30 d have been referred to as “tapered” regions, theoptical mode transmitted therein towards an end of the first device 10 cto 10 d adjacent to second device (not shown) actually flares.

Referring now to FIGS. 2( a) and (b), there is illustrated an integratedoptical device generally designated 5 e, according to a fifth embodimentof the present invention. The device 5 e provides first and seconddevices 10 e, 15 e optically coupled one to the other and formed infirst and second different material systems, the first device 10 ehaving a Quantum Well Intermixed (QWI) region 20 e adjacent a couplingregion 21 e between the first and second device 10 e, 15 e. As can beseen from FIGS. 2( a) and (b) a waveguide 23 e of the first device 10 ecomprises a tapered curved region 30 e adjacent a coupling region 21 ebetween the first and second devices 10 e, 15 e. Further, ananti-reflection coating 25 e is provided within the coupling region 21 eon an end facet of the first device 10 e. Also, a passive waveguide 16 eof the second device 15 e is complementarily curved to the portion 30 eso as to also assist in optical coupling between the first and seconddevices 10 e, 15 e.

Referring now to FIGS. 3 and 4, there is illustrated a sixth embodimentof a first device generally designated 10 f according to the presentinvention. Like parts of the device 10 f are identified by the samenumerals as for the device 10 a of the first embodiment of FIG. 1( a),but suffixed “f.”

The device 10 f comprises a GaAs substrate 50 f, upon which are grown anumber of epitaxial layers by known growth techniques such as MolecularBeam Epitaxy (MBE) or Metal Organic Chemical Vapour Deposition (MOCVD).The layers comprise a first 0.51 μm to 1 μm n-doped Al_(0.50)Ga_(0.50)Aslayer 55 f, a second 5 μm n-doped Al_(0.40)Ga_(0.60)As layer 60 f, athird 0.5 μm substantially intrinsic Al_(0.20)Ga_(0.80)As core layer,including a 10 nm GaAs Quantum Well (QW), 70 f as grown. On the corelayer 65 f is grown a 1 μm p-doped Al_(0.40)Ga_(0.60)As layer 75 f, andfinally on that layer is grown a p+ doped GaAs capping contact layer 80f. As can be seen from FIG. 3, a ridge waveguide 23 f is formed in thelayers 75 f, 80 f by known photolithographic techniques. Further in thisembodiment, a second broader ridge or mesa 35 f is also formed in thelayers 65 f and 60 f. Thus the ridge waveguide 23 f comprises a primarywaveguide while the mesa 35 f comprises a secondary waveguide. Thedevice 10 f also includes a tapered region 30 f on the waveguide 23 f.The device 10 f, therefore, acts as a mode converter converting a modefrom the device 10 f coupled to a second device (not shown), or a modetransmitted from the second device to the first device 10 f.

As can be seen from FIG. 3, contact metallisations 40 f and 45 f may beprovided on a top of ridge 23 f and an opposing surface of the substrate50 f. Further, as can be seen from FIG. 4, the device 10 f includes aQuantum Well Intermixed (QWI) region 20 f adjacent to the end of thedevice corresponding to the tapered region 30 f.

In this embodiment the Quantum Well Intermixed (QWI) region 20 f isformed in the first device 10 f by intermixing the Quantum Well 70 f inthe layer 60 f within the region 20 f by Impurity Free VacancyDiffuision (IFVD). When performing IFVD upon a top cap layer 80 f of theIII-V semiconductor material comprising the first device 10 f, there isdeposited a dielectric, e.g. Silica (SiO₂), layer of film. Subsequentrapid thermal healing of the semiconductor material causes bonds tobreak within the semiconductor alloy and e.g. Gallium ions oratoms—which are susceptible to Silica (SiO₂)—to dissolve into the Silicaso as to leave vacancies in the cap layer 80 f. The vacancies thendiffuse through the semiconductor material inducing layer intermixing,e.g. in the Quantum Well 70 f.

Referring now to FIG. 5 and to Table 1, there is illustrated a seventhembodiment of a first device generally designated 10 g, for use in anoptically integrated device according to the present invention. In thissixth embodiment, the first device 10 g is fabricated in Indium GalliumArsenide Phosphide (In In_(1-x) Ga_(x) As_(y) P_(1-y)).

The layer structure, grown on an Indium Phosphide (InP) substrate 50 g,is shown in Table 1 below.

TABLE I Thickness Repeats (A) Material x y Dopant Type 1 1000 In(x)GaAs0.53 Zn p 1 500 Q1/18 Zn p 1 11500 InP p 1 50 Q1.05 i 1 2500 InP 1 800Q1.1 i 1 500 QI.8 i  5* 120 Q1.26 i  5* 65 In(x)GaAs 0.53 i 1 120 Q1.26i 1 500 Q1.18 i 1 800 Q1.1 i 1 50000 Q1.05 Si n 1 10000 InP (buffer Si nlayer adjacent substate) *Quantum Well (QW) structure Q = Quaternary,e.g. Q1.1 = quaternary with 1.1 μm bandgap

As can be seen from FIG. 5, the first device 10 g includes an activewaveguide 23 g and adjacent to coupling region to a second device (notshown) a tapered region 30 g. The waveguide 23 g comprises a primarywaveguide of the first device 10 g, while a further ridge or mesa 35 gformed on the device 10 g comprises a secondary waveguide. In use, theoptical radiation generated within or transmitted from the waveguide 23g towards the tapered region 30 g as an optical mode, is caused upontransmission through region 30 g from primary optical guiding layer 65 ginto layer 60 g for optical coupling to second device (not shown).

The first devices 10 f and 10 g illustrate a design of regrowth-freetapered waveguide coupler. The small rib waveguide 23 f, 23 g is locatedon top of a thick lower cladding layer 60 f, 60 g that is partiallyetched to form mesa wave guide 35 f, 35 g. When the small rib 23 f, 23 gis sufficiently wide, the fundamental optical mode is confined to thesmall rib 23 f, 23 g, and there is a high confinement of light withinthe undoped waveguide core layer 65 f, 65 g (which itself contains theactive Quantum Well layers, e.g. 75 f in FIG. 3, or intermixed region 20f, 20 g). At the other extreme, when the small rib 23 f, 23 g issufficiently narrow, the fundamental mode expands to fill the largermesa waveguide 35 f, 35 g. This behaviour is a consequence of the designof the waveguide layers. The thicknesses and compositions of the QuantumWell layers at the top of the mesa 35 f, 35 g, and extending under thesmall rib 23 f, 23 g are such as to prevent guiding of light withinthese layers if the upper layers comprising the small rib 23 f, 23 g areetched away. The resulting waveguide allows-separate optimisation of theoptical mode properties of the rib 23 f, 23 g and mesa 35 f, 35 gwaveguides at the two extremes of rib width. At large rib widthshigh-performance device action (such as optical amplification, opticaldetection, electro-absorptive or electro-refractive modulation) can beachieved. At small rib widths the dimensions of the large mesa 35 f, 35g and thickness of the lower cladding materials establish the opticalmode size of the mesa waveguide for optimum coupling to passive Silicawaveguides. The expanded mode can be designed for optimum couplingdirectly to single mode waveguides in the second (non-semiconductor)material or to optical fibre, including 1.3 μm and 1.5 μmtelecommunication fibre.

The layer structure shown in FIG. 3 would be used to make a first device10 f with Quantum Wells resonant with radiation at a wavelength ofaround 860 nm. The structure shown in FIG. 5 would be used to make afirst device 10 g with Quantum Wells resonant with radiation at awavelength around 1.5 μm.

It will be appreciated that the embodiments of the inventionhereinbefore described are given by way of example only, and are notmeant to limit the scope thereof in any way.

It will he particularly understood that the device of the presentinvention is easier and simpler to manufacture than other devices, andtherefore provides the potential of obtaining high quality devices atreduced cost.

It will also be appreciated that in the disclosed embodiments the modematching means comprised a “tapered” waveguide providing a linear ornon-linear change in width, in modified implementations the change inwidth may be “periodically” or “a-periodically” segmented. Theexpression “segmented waveguide” is intended to encompass any waveguideinto which has been introduced a disturbance or variation in therefractive index of the waveguide along at least one dimension of thewaveguide. The variation may be periodic or, more preferably, aperiodic.Preferably the variation is along the longitudinal axis of thewaveguide. However, variations along the lateral axis, or even along anaxis oblique to the longitudinal axis may be used.

It will further be understood that in this invention, Quantum WellIntermixing (QWI) is used to reduce absorption by the Quantum Welllayers within the taper region and so reduce optical losses in the taperregion and improve device efficiency.

Finally, it will be appreciated that in a modification the first devicemay be inverted with respect to the second device, i.e. the ridgewaveguide of the first device may be in contact with, or adjacent, asurface of the second device.

1. An integrated optical device, comprising: a first device formed in afirst material system, said first material system being a III-Vsemiconductor material; and a second device formed in a second materialsystem, said second material system being other than a III-Vsemiconductor material; wherein said first device and said second deviceare optically coupled to each other so as to form an optical interfacebetween said first device and second device, and wherein said firstdevice defines a quantum well intermixed (QWI) re gion at or adjacentsaid optical interface that is effective to alter opticalcharacteristics of light passing through the first device.
 2. Anintegrated optical device according to claim 1, wherein said III-Vsemiconductor material includes at least one of: Gallium Arsenide(GaAs), Aluminum Gallium Arsenide (AlGaAs), Indium Phosphide (InP),Gallium Arsenide Phosphide (GaAsP), Aluminum Gallium Arsenide Phosphide(AlGaAsP), and Indium Gallium Arsenide Phosphide (InGaAsP).
 3. Anintegrated optical device according to claim 1, wherein said secondmaterial system is other than a III-V semiconductor material.
 4. Aninterated optical device according to claim 1, wherein said firstrefractive index is about 3.6, and said second refractive index is about1.5.
 5. An integrated optical device according to claim 1, wherein saidsecond material system is selected from: Silica (SiO₂), Silicon (Si),Lithium Niobate (NiNbO₃), a polymer, and a glass.
 6. An integratedoptical device according to claim 1, wherein said second material systemis doped with an optically active material.
 7. An integrated opticaldevice according to claim 1, wherein said first device includes anoptically active device.
 8. An integrated optical device according toclaim 7, wherein said optically active device is one of a laser diode, alight emitting diode (LED), an optical modulator, an optical amplifier,an optical switch, and an optical detector.
 9. An integrated opticaldevice according to claim 1, wherein said second device includes anoptically passive device.
 10. An integrated optical device according toclaim 9, wherein said optically passive device is a passive waveguide.11. An integrated optical device according to claim 1, furthercomprising an anti-reflection means disposed at said optical interface.12. An integrated optical device according to claim 11, wherein saidfirst device includes a facet at said optical interface, and saidanti-reflection means includes an anti-reflection coating on said facet.13. An integrated optical device according to claim 11, wherein saidfirst device and said second device are adapted to cooperate such that afirst direction of optical transmission is established at said opticalinterface, and further wherein first device includes a facet at saidoptical interface, said second device includes a facet at said opticalinterface, and said anti-reflection means includes said respectivefacets of said first and second devices being formed at an acute angleto an said first direction of optical transmission.
 14. An integratedoptical device according to claim 1, wherein said first optical deviceincludes a first waveguide adjacent said optical interface, said secondoptical device includes a second waveguide adjacent said opticalinterface, and said first and second waveguides include respectivecurved extents.
 15. An integrated optical device according to claim 1,wherein said integrated optical device operates in a wavelength range ofone of from about 600 nm to about 1300 nm, and from about 1200 nm toabout 1700 nm.
 16. An integrated optical device according to claim 1,wherein said first and second devices are formed on a common substrate.17. An apparatus including at least one integrated optical deviceaccording to claim
 1. 18. An apparatus in accordance with claim 17,wherein said apparatus is a circuit selected from an integrated opticalcircuit, an optoelectronic integrated circuit, and a photonic integratedcircuit.
 19. An integrated optical device, comprising: a first deviceincluding a first material system, and a second device including asecond material system, said second material system being different fromsaid first material system; wherein said first device and said seconddevice are optically coupled to each other so as to form an opticalinterface between said first device and second device, and wherein saidfirst device further includes a coupling region adjacent said opticalinterface containing an intermixed quantum well, said quantum wellintermixing (QWI) being effective to alter the optical characteristicsof light passing through the first device in said coupling region so asto provide for substantial mode matching between said first and seconddevices.
 20. An integrated optical device according to claim 19, whereinsaid first material system is a III-V semiconductor material.
 21. Anintegrated optical device according to claim 20, wherein said III-Vsemiconductor material includes at least one of: Gallium Arsenide(GaAs), Aluminum Gallium Arsenide (AlGaAs), Indium Phosphide (InP),Gallium Arsenide Phosphide (GaAsP), Aluminum Gallium Arsenide Phosphide(AlGaAsP), and Indium Gallium Arsenide Phosphide (InGaAsP).
 22. Anintegrated optical device according to claim 19, wherein said secondmaterial system is other than a III-V semiconductor material.
 23. Anintegrated optical device according to claim 19, wherein said secondmaterial system is selected from: Silica (SiO₂), Silicon (Si), LithiumNiobate (NiNbO₃), a polymer, and a glass.
 24. An integrated opticaldevice according to claim 19, wherein said second material system isdoped with an optically active material.
 25. An integrated opticaldevice according to claim 19, wherein said first device includes anoptically active device.
 26. An integrated optical device according toclaim 25, wherein said optically active device is one of a laser diode,a light emitting diode (LED), an optical modulator, an opticalamplifier, an optical switch, and an optical detector.
 27. An integratedoptical device according to claim 19, wherein said second deviceincludes an optically passive device.
 28. An integrated optical deviceaccording to claim 27, wherein said optically passive device is apassive waveguide.
 29. An integrated optical device according to claim19, wherein said coupling region includes a waveguide provided in saidfirst device, said waveguide being tapered so as to provide at least oneof: a linear change in width, a non-linear change in width, a periodicsegmentation, and an a-periodic segmentation.
 30. An integrated opticaldevice according to claim 19, further comprising an anti-reflectionmeans disposed at said optical interface.
 31. An integrated opticaldevice according to claim 30, wherein said first device includes a facetat said optical interface, and said anti-reflection means includes ananti-reflection coating on said facet.
 32. An integrated optical deviceaccording to claim 30, wherein said first device and said second deviceare adapted to cooperate such that a first direction of opticaltransmission is established at said optical interface, and furtherwherein first device includes a facet at said optical interface, saidsecond device includes a facet at said optical interface, and saidanti-reflection means includes said respective facets of said first andsecond devices being formed at an acute angle to an said first directionof optical transmission.
 33. An integrated optical device according toclaim 19, wherein said first optical device includes a first waveguideadjacent said optical interface, said second optical device includes asecond waveguide adjacent said optical interface, and said first andsecond waveguides include respective curved extents.
 34. An integratedoptical device according to claim 19, wherein said integrated opticaldevice operates in a wavelength range of one of from about 600 nm toabout 1300 nm, and from about 1200 nm to about 1700 nm.
 35. Anintegrated optical device according to claim 19, wherein said first andsecond devices are formed on a common substrate.
 36. An integratedoptical device according to claim 19, wherein said first materialsystems has a refractive index of about 3.6, and said second materialsystem has a refractive index of about 1.5.
 37. An apparatus includingat least one integrated optical device according to claim
 19. 38. Anapparatus in accordance with claim 37, wherein said apparatus is acircuit selected from an integrated optical circuit, an optoelectronicintegrated circuit, and a photonic integrated circuit.